In recent years, introduction of home energy management system (HEMS) is progressing in which various home electronic devices are connected to a home network to manage the home electronic devices using information technology (IT), in order to manage a power consumption amount in response to environmental concerns, for example.
HEMS requires an accurate indoor position measurement technique to perform control such as switching ON/OFF the power sources of the home electronic devices according to a position of a user who uses the system.
The indoor position measurement technique includes a method for estimating a distance of a wireless terminal from a base station using characteristics, that is a receiving strength of a radio wave attenuates according to the distance from the base station as shown in FIG. 2, and then estimating an intersection point with a circle having a radius of the estimated distance and about a center of each base station as shown in FIG. 3.
There is also a technique to create an electric field strength map in which the electric field strength at each point is registered in advance and use it as user navigation (see Patent Literature (PTL) 1, for example).